Placing
Production made
bottles are not evenly thick all the way around. So they roll until
the heaviest part is at the bottom.
One way to avoid
any rolling in the kiln is to put the bottle on a level surface and
let it roll to the heavy side. Mark the up side so that you can
place it in the kiln with the heavy side down.
Some times though
the seam lines – which will show in the final piece – are in the
wrong place. To keep the seam lines to the side, you can place a
small piece of 0.5 mm fibre paper against each side of the bottle at
the base if you are working on a hard surface. On a softer surface, the weight of the bottle or a gentle push will sink it into the surface enough to avoid rolling.
The
distance to place bottles apart is important to know so they do not
become attached when several are slumped together.
You
can slump test bottles of various diameters to determine their final
width.
However,
if you wish to calculate the distances, The width of slumped bottles is approximately 1.6 times the diameter of the original bottle. If you
want the base of the bottle to be flat too, the final size will be
wider, dependent on the amount of glass in the base.
You
also need to leave some additional space than this calculated distance between bottles,
as the final size is narrower than the size when hot. You should
leave at least an additional 10 mm to each side of the bottle.
So
a 50 mm diameter bottle will become 80mm wide. You need an
additional 10 mm each side, so the spacing from the centre of one
bottle to the next should be at least 100 mm.
The
surface that you are slumping onto is important too.
You
can place the bottles on a sand base that has been dusted with kiln
wash powder. This has the advantage of allowing a gentle push into
the sand to prevent rolling. But it imparts a grainy texture to the
back.
You
can get a smoother surface by using whiting or sifted plaster that
has been screeded smooth. This also allows the bottle to be gently
pressed into the surface.
You
can use fibre papers as separators from the shelf, but they are
relatively expensive.
Kiln
wash works very well. It can provide a very smooth surface, but if
you want more texture, you can sprinkle some kiln wash through a
sieve over the shelf.
Is the math wrong here or am I misinterpreting something? 50mm apart from center to center would have these bottles touching each other????
ReplyDeleteYes, you are right. Not thinking about the various ways of interpreting what I meant. :-) It should read 100mm from centre to centre. I had meant 50mm from centre to space left for the next bottle. That was not said and it was not clear. Thanks for the correction.
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